Record carrier and apparatus enabling seamless playback

ABSTRACT

A record carrier stores audio data as audio tracks in audio files and associated management information. To avoid annoying clicks at the end or beginning of live recorded audio tracks, if those tracks are not played back seamlessly but by suppressing of introductory audio data stored in the pre-track, a seamless playback information is provided in the management information indicating if an audio track has to be played back seamlessly after a particular other audio track.

The present invention relates to a record carrier comprising audio dataas audio tracks in audio files and associated management information.Further, the present invention relates to a recording apparatus andmethod of recording audio data on such a record carrier as well as aplayback apparatus and method of reading audio data stored on such arecord carrier for playback.

CD players can quickly show how many audio tracks there are on the discsand how much time each audio track and the complete disc takes. Also MP3players make this possible by use of an index file. Without such anindex, the MP3 player would first have to scan all the directories,inspect each audio file, create a track file numbering and extract theplay time. Thus, the use of management information associated with theaudio data stored on a record carrier to present additional informationto the user, in particular the playing time of audio tracks, is known.

On a CD the audio data are stored from the beginning of the first audiotrack and to the end of the last audio track. In between most audiotracks recorded in a studio, there is a silence. The silence belongs tothe next audio track. Where this silence ends, and therefore, where themusic starts again, is also noted in the management information, inparticular in the table of contents (TOC) of a CD. In live recordings,there is usually sound in between the actual music. An audio trackusually ends with cheering, somebody might comment on the last song,start introducing the next song, and then the music starts again. Thetrack number usually increments somewhere in between, e.g. where theintroduction of the next song is done. However, the entry in the TOCusually points to the position right where the music starts. Whenplaying such a disc, the track number changes when the cheering for thelast song ends and the next song is introduced. But when pressing theoption “next track” at the player, it jumps to the position right wherethe music of the next song starts.

When generating MP3 audio tracks, a live recording has to be cut up intoindividual audio files. In the MP3 world as well as in the electronicmusic distribution (EMD) world, audio files are traded separately. AlsoMP3-like players play these audio files separately. They generallyintroduce themselves a pause in between audio files. Each individualaudio file has to be faded in, because otherwise, the sound starts witha click. Since live recording is a continuous recording, each individualaudio file also has to be faded out, since otherwise there would also bean annoying click at the end. Thus, a regular MP3 player cannot recreatethe exact experience of a live recording. Other situations where thisproblem appears are continuous recordings where one song moves on to thenext song without a break, such as a modern dance CD.

It is thus an object of the present invention to provide a recordcarrier as well as a corresponding recording and playback apparatus aswell as corresponding methods by which this problem can be avoided andwhich enable a better hearing experience, in particular when liverecordings or continuous recordings shall be played back.

This object is achieved according to the present invention by a recordcarrier to which the management information includes a seamless playbackinformation indicating if an audio track has to be played backseamlessly after a particular other audio track.

A corresponding recording apparatus comprises management informationupdate means for updating the management information when an audio trackis recorded on the record carrier by including a seamless playbackinformation indicating if the audio track has to be played backseamlessly after a particular other audio track.

A corresponding playback apparatus comprises management informationevaluation means for evaluating the seamless playback information byplaying back the read audio track seamlessly after the particular otheraudio track if the seamless playback information indicates that theaudio track has to be played back seamlessly after the particular otheraudio track.

The present invention is based on the idea to include a specific pieceof information into the management information which allows the playbackapparatus to determine if the next audio track has to be played backseamlessly after a certain other audio track or if this seamlessplayback mode is not required. When the seamless playback informationindicates that the audio track should be played back seamlessly, noartificial break or silence will be introduced by the playback apparatusin between audio tracks so that an annoying click at the start and/orend of a live recorded audio track will be avoided. Further,introductory audio data, such as cheering or introductory speech beforethe actual song in a live recording, will not be suppressed whenseamless playback is required. Thus, especially for live recordings, amuch better hearing experience will be the result.

According to an advantageous embodiment the management informationfurther comprises a transition effect information specifying thetransition effect to be applied during subsequent playback of two audiotracks. In particular, if playback of audio tracks must not beseamlessly, the effect in between the two audio tracks can be specified.Thus, a break, a cross-fade effect, a fade-in or a fade-out can, forinstance, be defined by this transition effect information.

It is further preferred that additionally an effect length informationindicating the length of said transition effect is included in saidtransition effect information.

As already mentioned, especially in live recordings, audio trackscomprise not only the song itself, referred to as main audio data in thefollowing, but also introductory audio data, such as cheering andintroductory speech, referred to as introductory audio data.

Each audio track in live recordings thus has a main track comprising themain audio data and, positioned in front of the main track, a pre-rackcomprising such introductory audio data which is to be played backbefore the main audio data in seamless playback mode. Of course, forinstance for studio recordings, the pre-track can also be empty.

In order to provide the user with an information about the length of thepre-track and/or to enable the playback apparatus to jump immediately tothe start of the main track, even during playback of the pre-track, anadditional pre-track information is included in the managementinformation indicating the length of the pre-track. Thus, by use of the“next track” option of the playback apparatus the user can instruct theplayback apparatus to immediately jump to the start of the main trackand to suppress playback of the introductory audio data, also in aseamless playback mode.

The management information is preferably stored in a separate index filestored on the record carrier as part of the administrative data.However, it is also possible to store part or all of the managementinformation in a play list, which can also be defined by a user.

The management information can also be updated when adding or deletingan audio track. An extra help when adding an audio track is an albuminformation additionally included in the management informationaccording to a preferred embodiment which indicates the album to whichan audio track is assigned if the audio tracks are assigned to one ormore albums on the disk. Thus, when a new audio track is added, therecording apparatus can easily find out whether there are already audiotracks from the same album on the disc and where to add the presentaudio track.

In a still further embodiment the management information comprises adatabase file including records of additional information related toaudio tracks stored on the record carrier. Thus, a lot of textual andnumerical information on all audio tracks can be stored on the recordcarrier in such a database file. This database file also allows theadditional further records when storing further audio tracks on therecord carrier. When an audio track is deleted from the record carrier,the corresponding record in the database file is preferably simplymarked as invalid.

The present invention will now be explained in more detail withreference to the drawings in which

FIG. 1 shows the layout of a record carrier according to the presentinvention sequentially,

FIG. 2 shows the track structure of an audio track, according to theinvention,

FIG. 3 shows an example of the structure of an index file, according tothe invention,

FIG. 4 shows a table illustrating transition effect information,according to the invention,

FIG. 5 shows a table defining different effect types, according to theinvention,

FIG. 6 shows a simple block diagram of a recording apparatus accordingto the invention and

FIG. 7 shows a simple block diagram of a playback apparatus according tothe invention.

As shown in FIG. 1 audio data in the form of audio tracks t1, t2, . . ., tx (these can be regarded as sub-areas of an audio data area t) can bestored on the record carrier as separate audio files. Such audio filesare preferably readable and transferable by a computer, and can beplayed back by a consumer electronics device but also by a driveincluded in a PC. In addition to the audio data associated managementinformation m1, m2, . . . , mx (these can be regarded as sub-areas of amanagement area m) is also stored on a record carrier, preferably in apredetermined area provided for these purposes. As can be seen from FIG.1, for each audio track t an entry m in the management information areais provided.

The track structure of an audio track according to the present inventionis shown in FIG. 2. As can be seen the audio track t comprises apre-track pt and a main track mt. The total play time p is the play timeof the pre-track pt and the main track mt together. The pre-track ptmainly comprises introductory audio data, such as cheering orintroductory speech in a live recording, while the main track mtessentially comprises the song itself. By use of an entry time indicatore the playback apparatus can jump immediately to the start of the maintrack mt if a user does not want to hear the introductory audio data butimmediately wants to have the main track mt to be played back. However,if a seamless playback mode is selected by a user or if a seamlessplayback information which will be explained in detail below indicatesthat the present track t needs to be played back seamlessly right fromthe start, the pre-track pt is also played back.

FIG. 3 shows an embodiment of an index file used according to thepresent invention for storing management information. In the variouscolumns besides the syntax the number of bytes (# bytes), the mnemonicand an exemplary value are given in this table. The fields will beexplained in the following.

The end_code includes a 4-byte hexadecimal number with a value of0x00000000 that indicates the termination of the structure of the indexfile index( ).

Spec_version is a 2-byte number showing the version number of theformat.

The field index_signature shall be filled with a particular string usedas signature.

The asset_ID contains the asset ID of an audio file. All asset IDspresent in the index file shall be unique, i.e. they are not allowed toappear more than once. The order in which asset IDs appear in the indexfile is not prescribed. The value of 0x00000000 is not allowed.

The album_number contains the number assigned to the album that containsthe audio file which is indicated by the previous field asset_ID. Theorder in which album numbers appear in the index file is not prescribed.A value of 0x0000 is not allowed.

The track_number contains the track number of the audio file within thealbum indicated in the previous field album_number. It is also called“position”. The order in which track numbers appear in the index file isnot prescribed. A value of 0x00000000 is not allowed.

The play_length contains the total play time of the main audio stream inthe audio file.

The entry_time contains the length of the pre-track pt of the audiostream in the audio track.

The transition_effect contains the transition effect to be appliedbetween the previous audio track and the present audio track, when audiotracks are played in the order of the index file. This field will beexplained in more detail below with reference to FIGS. 4 and 5.

The bundle_ID_hash contains the hash of the bundle ID of the audio file.The hash function to be used is preferably the CRC-32 hash as defined inISO 8802-3:1998(IEEE802.3) or POSIX1003.2.

The mix_no contains 0 in case the audio file contains one mix of theaudio data. In case the audio file contains more than one mix, e.g. astereo and a multi-channel mix, the index file shall contain entries foreach of these mixes. The field mix_no will be used to identify thesemixes. Numbering shall start at 0 and be incremented by 1 for eachadditional mix.

The end_code_location holds the value of end_code that indicates thetermination of the index file structure.

The mnemonics used in the table have the following meaning: “bslbf”means “Bit Sequence Left Bit First” which must be interpreted as a bitstream. The term “uimsbf” means “Bit Sequence Most Significant BitFirst” which must be interpreted as unsigned integer (so multi-byteintegers have most significant byte first).

The transition effect field is defined in the table shown in FIG. 4. Theterm “previous track” here means the previous track when audio tracksare played in the order of the index file or in the order of one ofseveral audio play lists which can be defined by users. The meanings ofthe fields defined for the transition effect are as follows:

The play_pre_track determines where to start playing this audio trackwhen audio tracks are played in the order of the index file or ifseamless playback mode shall be used, i.e. this field actually indicatesif this audio track shall be played seamlessly after a particular otheraudio track, which is for instance important for live recordings. Ifthis field has the value 1, then this audio track shall be playedincluding the pre-track, i.e. seamlessly from relative time 0 (see FIG.2). If this field has the value 0, then this audio track shall be playedfrom entry time e, i.e. only the main track mt shall be played back.

The effect_type contains the effect to be applied in between theprevious audio track and the start of the present audio track, asdetermined by the value of play_pre_track. The effects are defined andexplained in the table shown in FIG. 5. Possible effects are thussilence, cross-fade or no effect. Of course, further effects can bedefined as well.

The effect_length indicates the length of the effect defined ineffect_type.

A block diagram of a recording apparatus 10 according to the presentinvention is shown in FIG. 6. Inputted audio data A is recorded on adisc D by an audio recording unit 11. Additionally, managementinformation associated with the recorded audio data is updated by amanagement information update unit 12. Thus, for instance, when newaudio tracks are added for storage on the disc D, simply a new record isadded to the index file or, preferably, to a larger additional databasefile 50 comprising numerical and textual information regarding thestored audio data and being much larger than the index file. Also, if anaudio track is deleted from the record carrier D, the managementinformation will be updated, e.g. by simply marking a record in themanagement information area as invalid. This allows for in-place editingof files, which is an advantage over having to read or write the wholefile again.

A simple block diagram of a playback apparatus 20 according to thepresent invention is shown in FIG. 7. Data are read from the disc D by areading unit 21. Further, related management information is also readand evaluated by a management information evaluation unit 22. Inparticular, based on the read management information the transitioneffect for the transition from a previous audio track to the presentaudio track will be determined, e.g. if a silent break shall beintroduced or not or if a cross-fade effect shall be applied. Based onthe read play_pre_track information stored in the management informationit will further be decided if a seamless playback must be applied, i.e.if the pre-track pt must be played back or not which is important forlive recordings to avoid annoying clicks at the end or the beginning ofa live recorded audio track. Thus a much better hearing experience willbe enabled by the playback apparatus according to the present inventionevaluating such management information.

1. A record carrier comprising audio data as audio tracks in audio filesand associated management information, said management informationcomprising seamless playback information indicating if an audio trackhas to be played back seamlessly after a particular other audio track,wherein said audio track comprises a main track and a pre-track, saidmain track comprising main audio data and said pre-track comprisingintroductory audio data to be played back before the main audio data ina seamless playback mode, and wherein said management informationcomprises pre-track information indicating a length of the pre-track. 2.The record carrier as claimed in claim 1, wherein said managementinformation further comprises transition effect information specifying atransition effect to be applied during subsequent playback of two audiotracks.
 3. The record carrier as claimed in claim 2, wherein saidtransition effect information comprises effect length informationindicating a length of the transition effect.
 4. The record carrier asclaimed in claim 1, wherein said management information is stored as aseparated index file or is included in a play list.
 5. The recordcarrier as claimed in claim 1, wherein the audio track is assigned toone or more albums and wherein the management information comprisesalbum information indicating an album to which the audio track isassigned.
 6. The record carrier as claimed in claim 1, wherein saidmanagement information further comprises a database file comprisingrecords of additional information related to audio tracks stored on therecord carrier, said database file allowing addition of further recordswhen storing further audio tracks on the record carrier and marking ofrecords as invalid when deleting audio tracks.
 7. A recording apparatusfor recording audio data as audio tracks in audio files and associatedmanagement information on a record carrier, comprising audio recordingmeans for recording an audio track and said management information onthe record carrier, the apparatus further comprising managementinformation update means for updating said management information byincluding seamless playback information indicating if the audio trackhas to be played back seamlessly after a particular other audio track,wherein said audio recording means is adapted for recording said audiotrack comprising a main track and a pre-track, said main trackcomprising main audio data and said pre-track comprising introductoryaudio data to be played back before the main audio data in a seamlessplayback mode, and wherein said management information update means isadapted for updating said management information by including pre-trackinformation indicating a length of the pre-track.
 8. The recordingapparatus as claimed in claim 7, wherein said management informationupdate means is adapted for updating said management information byincluding transition effect information specifying a transition effectto be applied during subsequent playback of two audio tracks.
 9. Therecording apparatus as claimed in claim 8, wherein said managementinformation update means is adapted for updating said managementinformation by including effect length information indicating a lengthof the transition effect.
 10. The recording apparatus as claimed inclaim 7, wherein said audio recording means is adapted for recordingsaid management information as a separated index file or included in aplay list.
 11. The recording apparatus as claimed in claim 7, the audiotrack being assigned to one or more albums, wherein said managementinformation update means is adapted for updating said managementinformation by including album information indicating an album to whichthe audio track is assigned.
 12. The recording apparatus as claimed inclaim 7, wherein said management information update means is adapted forupdating said management information by including a database filecomprising records of additional information related to audio tracksstored on the record carrier.
 13. A method of recording audio data asaudio tracks in audio files and associated management information on arecord carrier, wherein said management information is updated when anaudio track is recorded on the record carrier by including a seamlessplayback information indicating if the audio track has to be played backseamlessly after a particular other audio track, wherein the audio trackcomprises a main track and a pre-track, said main track comprising mainaudio data and said pre-track comprising introductory audio data to beplayed back before the main audio data in a seamless playback mode, andwherein said management information comprises pre-track informationindicating a length of the pre-track.
 14. A playback apparatus forreading audio data stored as audio tracks in audio files and associatedmanagement information from a record carrier and for playback of a readaudio track, said management information including seamless playbackinformation indicating if the audio track has to be played backseamlessly after a particular other audio track, the apparatuscomprising reading means for reading the audio track and said managementinformation from the record carrier, the apparatus further comprisingmanagement information evaluation means for evaluating said seamlessplayback information by playing back the read audio track seamlesslyafter the particular other audio track in dependence of the seamlessplayback information, wherein said reading means is adapted for readingsaid audio track comprising a main track and a pre-track, said maintrack comprising main audio data and said pre-track comprisingintroductory audio data to be played back before the main audio data ina seamless playback mode, and wherein said management informationevaluation means is adapted for evaluating pre-track informationindicating a length of the pre-track, said pre-track informationcomprised in said management information.
 15. The playback apparatus asclaimed in claim 14, wherein said management information evaluationmeans is adapted for evaluating transition effect information specifyinga transition effect to be applied during subsequent playback of twoaudio tracks, said transition effect information comprised in saidmanagement information.
 16. The playback apparatus as claimed in claim15, wherein said management information evaluation means is adapted forevaluating transition effect information comprising effect lengthinformation indicating a length of the transition effect.
 17. Theplayback apparatus as claimed in claim 14, wherein said reading means isadapted for reading said management information as a separated indexfile or included in a play list.
 18. The playback apparatus as claimedin claim 14, the audio track being assigned to one or more albums,wherein said management information evaluation means is adapted forevaluating album information indicating an album to which the audiotrack is assigned, said album information comprised in said managementinformation.
 19. The playback apparatus as claimed in claim 14, whereinsaid reading means is adapted for reading a database file comprisingrecords of additional information related to audio tracks stored on therecord carrier, said database comprised in said management information.20. A method of reading audio data stored as audio tracks in audio filesand associated management information from a record carrier and ofplayback of the read audio track, said management information includinga seamless playback information indicating if the read audio track hasto be played back seamlessly after a particular other audio track,wherein said seamless playback information is evaluated by playing backthe read audio track seamlessly after the particular other audio trackin dependence of the seamless playback information, wherein the readaudio track comprises a main track and a pre-track, said main trackcomprising main audio data and said pre-track comprising introductoryaudio data to be played back before the main audio data in a seamlessplayback mode, and wherein said management information comprisespre-track information indicating a length of the pre-track.